They now also have a nice solution to my 'problem' with a large collection of tracks on the external USB drive plugged into the back of the WiiM Amp. The latest version of their App caches and 'resyncs' the scanned metadata from the tracks found on the usb. So both the WiiM Amp itself and now also the mobile app caches the information - this makes it very fast and reasonable good search capability (though of course it is not a 'Roon level' UI)